1. Field of the Invention
The present invention relates to adhesives comprising silicone ionomers for numerous applications, particularly for healthcare applications.
2. Background of the Art
The U.S. Pat. No. 5,232,702 describes pressure sensitive silicone adhesive compositions prepared by the addition of a silicate resin to a silicone fluid, along with a cohesive strengthening agent. The cohesive strengthening agent improves adhesive-substrate adhesion and reduces cold flow. Examples of cohesive strengthening agents include nonionic surfactants, fatty acid esters, metallic salts of fatty acids, phosphoric acid, carbonic acid, polysaccharides, carboxypolymethylene, PVP, PVA and precipitated amorphous silica. However, the invention makes no mention of adhesive hydrophilicity.
The European Patent No. 0312265 describes randomly grafted polymers of polyethylene glycol and siloxane, with the polyethylene glycol segment containing a maximum of 15 ethylene oxide units. The silicone adhesive of the present composition involves simple blending of the said polymer with silicone resin, with an optional curing step. The presence of ethylene glycol increased the hydrophilicity and water uptake of the adhesive but compromised its adhesive strength. Increasing the resin content of the adhesive brought back the adhesive strength, but reduced its water uptake. Thus, the hydrophilicity and adhesive nature of the object of this invention were mutually exclusive. Further, there was no mention of increased breathability of the adhesive composition on account of PEG addition.
WO Patent Publication No. 2010124187 describes pressure sensitive adhesives that are silicone-acrylate hybrids, and are prepared by covalent attachment of an acrylate-functional pre-polymer during the condensation crosslinking between silicate resin and gum. Due to the absence of residual acrylate monomers, such a composition is especially useful for skin contact applications. The covalent attachment of the acrylate prepolymer to the silicone adhesive occurs via end-capped alkoxysilane or halosilane groups.